JPH047150A - Laminated material for packing food, food packing container composed thereof and production or the container - Google Patents

Abstract

PURPOSE:To obtain an inexpensive container having excellent heat resistance and food preservability and also excellent in structural strength by heating a laminated material consisting of an extremely thin C-PET film layer and other heat-resistant resin layer to the crystallization temp. of the C-PET film layer to mold the same. CONSTITUTION:A polyphenylene ether resin, a foaming agent and a nucleating agent are kneaded and cooling using a tandem extruder and extruded from a circular die to obtain a polyphenylene ether resin foamed sheet. C-PET is extruded from a T-die using an extruder and cooled by a chilled roll to obtain a C-PET film. The polyphenylene ether resin foamed sheet and the C-PET film are laminated at temp. (110 - 120 deg.C) not substantially crystallizing the C-PET film using a hot melt type polyester special sealant as the binder to obtain a laminated sheet. This laminated sheet is molded by a single-shot vacuum pressure forming machine whose mold temp. on the side coming into contact with the C-PET film layer is adjusted to 165 deg.C to obtain a container wherein a peripheral wall (2) is erected from the peripheral edge of a bottom plate (1).

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is inexpensive and has excellent heat resistance, hot water resistance, sealing performance, and gas barrier properties, and can be used as a packaging material for retort foods and microwave-heated foods, or in microwave ovens and ovens. The present invention relates to a laminated material suitable as a heatable dual ovenable packaging material, a food packaging container made of the material, and a method for manufacturing the container.

[Prior art and problems]

In recent years, instant foods such as retort foods, chilled foods, and frozen foods have made remarkable progress along with the spread of microwave ovens and ovens, and have become deeply entrenched in our daily lives.

By the way, these food packaging materials are low in cost, have sufficient heat resistance against heat sterilization treatment, microwave ovens, and oven heating, and have hot water resistance, sealing properties, and gas barrier properties to retain food flavor. It is necessary to have storage stability and structural strength as a container.

Conventionally, materials for these food packaging containers include laminates of heat-resistant polystyrene foam sheets and films made of polypropylene, polystyrene, polyethylene terephthalate (hereinafter referred to as PET), filled polypropylene, and crystalline polyethylene terephthalate. (hereinafter referred to as C-PET) etc. are used.

However, laminates such as polystyrene foam sheets and polypropylene films do not have sufficient heat resistance, and cannot be used in retort food containers that are sterilized at high temperatures (130-140°C) or heated above 130°C in microwave ovens. It is unsuitable as a food container.

Also, in the case of filler-containing polypropylene, it has the same problems as above, such as insufficient heat resistance and low food preservation properties (gas barrier properties).

Furthermore, C-PET is often used with a thickness of 400 to 1500 μm, and although it has good heat resistance and food storage stability, the cost of C-PET itself is high, and it cannot be thermoformed. The crystallization time is long, 6 to 8 seconds, and the length of this molding cycle has the disadvantage that it is difficult to provide inexpensive containers. These food containers are usually one-way (disposable) and therefore their high cost is a fatal drawback.

As mentioned above, the packaging materials that have been put to practical use so far all have their advantages and disadvantages, and the reality is that no one that is fully satisfactory has yet been proposed.

In view of these circumstances, the present invention aims to provide a laminated material for food packaging, a food packaging container, and a method for manufacturing the container, which is inexpensive, has excellent heat resistance and food preservation properties, and has excellent structural strength. purpose.

[Means for solving problems]

In order to achieve the above objective, the inventors of the present invention conducted extensive research and found that by making the expensive C-PET film layer as thin as possible and laminating it with other relatively inexpensive heat-resistant resin layers, the cost of the material itself was reduced. The present invention has been completed based on the discovery that the molding cycle can be shortened and high-quality laminated materials and packaging containers can be provided at low cost.

That is, the first aspect of the present invention is a laminated material for food packaging consisting of an ultra-thin C-PET film layer and another heat-resistant resin layer, and the second aspect of the present invention is a C-PET film of the above laminated material. The third aspect of the present invention is a food packaging container formed by crystallizing layers.
Each content is a method of manufacturing a food packaging container, characterized in that the laminated material described above is heated to the crystallization temperature of the C-PET film layer and then molded.

The C-PET used in the present invention is PET whose crystallinity is improved by blending an inorganic salt such as calcium carbonate or magnesium carbonate or a polyolefin crystal nucleating agent, and its heat resistance is significantly improved by thermoforming. Specific product names include, for example, "Tenite" manufactured by Eastman Kodak, "Pet Max" manufactured by Toyobo Betcord, and "Arnite J" manufactured by Akzo.The C-PET film layer is extremely thin and is preferably is 500 μm or less, more preferably 400 μm or less, even more preferably 20 to 300 μm. Particularly, the thickness often used in the present invention is 30 to 2 μm.
The thickness is preferably 00 μm, and more preferably 50 to 150 μm.

Other heat-resistant resins (other than C-PET) used in the present invention are not particularly limited, such as polypropylene (
(with filler), PET, polycarbonate, polyetherimide, polysulfone, polyphenylene ether, polyarylate (PAR), polycyclohexylene dimethylene terephthalate (PCT), etc., and these may be used alone or in combination of two or more types. The thickness is not particularly limited, but in order to provide structural strength as a container, it is preferably 0.211 Im or more, and 0.41 Im or more.
The above is more preferable.

It is preferable that the other heat-resistant resin layer is a foam. That is, during molding, heat transfer from the mold on the C-PET side is carried out by the heat-insulating effect of the other heat-resistant resin foam layer laminated on the opposite side. This is a highly preferred embodiment because the heating is effective and therefore, in combination with the thinness of the C-PET, crystallization proceeds rapidly and the molding cycle is significantly shortened. In addition, due to the insulating properties of the foam, the molded container itself does not get too hot immediately after cooking in the microwave or in the open, so it has the advantage that it can be carried by hand.

Further, by laminating a heat-sealable resin film layer on the surface of the C-PET film layer, top sealing becomes easy. Examples of such heat-sealable resins include polypropylene resins, polyester resins, ethylene-vinyl acetate copolymer resins, and polyurethane resins, and the thickness thereof is not particularly limited, but is 10 to 150 μm.
A range of m is preferred, and more preferably a range of 15 to 80 μm is used.

In addition, if polyester resin is used for the other heat-resistant resin layers, and more preferably polyester resin is used for the heat-sealable resin film layer, the paper plate burns with fewer calories than a paper plate and does not emit toxic gas. This is a preferred embodiment because it facilitates disposal and recycling.

The lamination of the above C-PET film layer and other heat-resistant resin, and the lamination of these and the heat-sealable resin film layer are performed by a known method such as thermal lamination or binder lamination, and the C-PET film layer is treated with a sealer. It can also be laminated. Furthermore, extrusion laminations (including coextrusion laminations) are also possible.

The laminated material obtained as described above is thermoformed by vacuum forming, pressure forming, or the like. As a result, the crystallization of the C-PET film layer is enhanced, the heat resistance is improved, and a food packaging container with excellent heat resistance that can be sterilized at high temperature and cooked in a microwave or oven is obtained.

By the way, if the obtained container is used for frozen food,
Although the heat resistance is sufficient as described above due to crystallization, the impact resistance strength at low temperatures is poor, and the impact resistance strength particularly at the edge of the container may become a problem.

To solve this problem, it is effective to control the heating temperature near the edge of the container to be below the crystallization temperature of C-PET to bring it into an uncrystallized or low-crystalline state.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by these in any way.

Example 1 Polyphenylene ether resin (Noryl@PPE
/PS・55/45. Made by GE PLASTIC5) 1
00 parts by weight and a blowing agent (butane/pentane/50150
) 5 parts by weight and 0.5 parts by weight of nucleating agent (talc) in 40 parts by weight.
~Kneaded using a 50φ tandem extruder, cooled, and extruded from a circular die to form a polyphenylene ether resin foam sheet (thickness 1.6 wn, density 0.09 g/cd)
I got it.

On the other hand, C-PET (Ten) with an intrinsic viscosity (IV) of 0.73
ite@9663. EASTMAN CHEMICA
A C-PET film with a thickness of 75 μm that is still in a substantially amorphous state (density 1.3428/cd or less) is made by extruding it from a T-die using a 45φ extruder and cooling it with a chilled roll. Obtained.

The above polyphenylene ether resin foam sheet and C-P
Using ET film and a hot melt type polyester special sealant as a binder, C-PET
The temperature at which the film does not substantially crystallize (110-120
A laminated sheet was obtained which was laminated at 10°C.

Example 2 Using the laminated sheet obtained in Example 1, the mold temperature on the side in contact with the C-PET film layer was adjusted to 165°C in a single-shot vacuum/pressure forming machine, as shown in Fig. 1. Bottom plate (1
) A container was molded in which a peripheral wall (2) was erected around the periphery of the container. Table 1 shows the heat resistance, etc. of the containers obtained by setting the retention time in the mold to 4 levels (Experimental Sewage ■■■■) of 3, 5, and 7.9 seconds.

Comparative Example 1 Single polyphenylene ether resin foam sheet (thickness:
1.6) and C-PET sheet alone (thickness near 50μ
m) was molded using a single-shot vacuum/pressure forming machine in the same manner as in Example 2, and the performance of each is shown in Table 1 as a comparative example (experimental sample).

From the results in Table 1, the heat resistance of the laminated container according to the present invention is as follows:
The container change rate is better than that of a single polyphenylene ether resin foam sheet container (experiment No. 2), and the degree of crystallinity can be increased in a shorter time than that of a single crystallized PET container (experiment No. 2). It can be seen that it has excellent heat resistance.

Example 3 The laminated material obtained in Example 1 was molded at a mold temperature of 175°C on the side in contact with the C-PET film layer, and at the ridge corner ( 3), and on the mold surface in contact with the C-PET film layer of the edge part (4) in contact with the peripheral wall (2), place a Teflon sheet (0.5 mm thick).
A container was molded in the same manner as in Example 2 using a single-shot vacuum/pressure molding machine having a mold embedded so that its surface was flush with the inner surface of the other mold. The heat resistance, low temperature drop impact strength, etc. of the obtained container are shown in Table 2.

As shown in Table 2, the laminated container according to the present invention (experimental
Regarding the heat resistance of ■), its container change rate is superior to that of a polyphenylene ether resin foam sheet single container (Experimental Seed ■), and the drop impact strength at low temperatures is that of a crystallized PET single container (Experimental Soh ■). Better.

Example 4 1 part by weight of polyarylate (PAR) resin [polycondensate of mixed terephthalic acid dichloride of terephthalic acid and isophthalic acid (50150) and 2,2-bis(4-hydroxyphenyl)propane] and epoxy system Compound 0.2
Parts by weight and blowing agent (butane/pentane/50150)
and 4 parts by weight of nucleating agent (calcium stearate).
Using a 5-50φ tandem extruder, the mixture was kneaded, cooled, and extruded from a circular die to obtain a foamed polyarylate resin sheet (thickness: 1.4 mm, density: 0.18 g/cj).

From the above polyarylate resin foam sheet and the C-PET film obtained in Example 1, a hot-melt type polyester special sealant agent was used as a binder to form a C-PET film.
The temperature at which the ET film does not substantially crystallize (110 to 1
A laminated sheet was obtained which was laminated at 20°C.

Example 5 Using the laminated sheet obtained in Example 4, a container was molded in the same manner as in Example 2. The holding time in the mold was set at two levels, 5 seconds and 7 seconds (experimental test α■ [phase]), and the heat resistance etc. of the obtained containers are shown in Table 3.

Comparative Example 2 Single polyarylate resin foam sheet (thickness: 1.8n
A container was molded from o) in the same manner as in Example 5, and its performance is shown in Table 3 as a comparative example (experimental stone ①).

As shown in Table 3, the laminated container according to the present invention (Experiment No.
■[Phase]) has better heat resistance than the polyarylate resin foam sheet single container (experiment Nα■) in its volume change rate, and crystallization occurs in a shorter time than the crystallized PET single container (experimental stage ■). It can be seen that as the temperature increases, it has excellent heat resistance.

Example 6 Using the laminated sheet obtained in Example 4, a container was molded in the same manner as in Example 3. Table 4 shows the heat resistance, low temperature drop impact strength, etc. of the obtained container.

As shown in Table 4, the laminated container according to the present invention (experimental
The heat resistance of @) is superior to that of the polyarylate resin foam sheet single container (experiment Nα ■) in terms of volume change rate.
In addition, the drop impact strength at low temperatures is superior to that of a single crystallized PET container (Experiment No. 2).

[Action/Effect]

As Soft says, the present invention not only reduces material costs by making the expensive C-PET film thinner, but also shortens the crystallization time of C-PET compared to conventional C-PET containers. The heat resistance is reduced to less than 1/2,
A laminated material for food packaging and a container for food packaging that have excellent food preservation properties can be provided at extremely low cost, and their usefulness is extremely high.

[Brief explanation of drawings]

FIG. 1 is a top view showing containers molded in Examples and Comparative Examples, and FIG. 2 is a cross-sectional view taken along the line X-x in FIG. 1. ■...Bottom plate 2...Peripheral wall 3.4...Ridge line part

Claims (1)

[Claims] 1. A laminated material for food packaging comprising an ultra-thin crystalline polyethylene terephthalate film layer and another heat-resistant resin layer. 2. The laminated material according to claim 1, wherein the crystalline polyethylene terephthalate film layer has a thickness of 500 μm or less. 3. The laminated material according to claim 1, wherein the other heat-resistant resin layer is made of a foam. 4. Claim 1, wherein a heat-sealable resin film layer is laminated on the surface of the crystalline polyethylene terephthalate film layer.
Laminated materials as described. 5. A food packaging container obtained by crystallizing the crystalline polyethylene terephthalate film layer of the laminated material according to claims 1 to 4. 6. The food packaging container according to claim 5, wherein the vicinity of the edge of the container is amorphous or low-crystalline. 7. A method for manufacturing a food packaging container, which comprises heating and molding the laminated material according to claims 1 to 4 to the crystallization temperature of the crystalline polyethylene terephthalate film layer. 8. The manufacturing method according to claim 7, wherein the heating temperature near the edge of the container is controlled to be below the crystallization temperature of the crystalline polyethylene terephthalate film layer to make the container non-crystalline or low-crystalline.